Federal prosecutors Sunday were poised to bring criminal charges against Boston Marathon bombing suspect Dzhokhar Tsarnaev, launching a process legal specialists said would unfold during many months and involve a number of critical, emotionally charged decisions.

Carmen Ortiz, the US attorney in Massachusetts, declined to say Saturday when charges would be brought, or which crimes would be included, but said her office was “formulating the charges.”

Chief among them are whether to seek the death penalty for the attacks, which killed three people and wounded more than 170; the potential consequence of authorities’ decision not to read Tsarnaev his Miranda rights; and whether Tsarnaev’s case would be moved outside Boston in order to assure a fair trial. State prosecutors may also file charges in the case.

Several lawyers noted that the trial of Timothy McVeigh, the bomber of the Oklahoma City federal building, was moved to Colorado.

“It’s six degrees of separation, like the Oklahoma bombing,’’ said Max D. Stern, a Boston defense attorney. “Everybody knows somebody who knows somebody that was injured or was there or was terrorized by what happened. Or everyone has been there, to the spot in the Marathon where it happened.’’

While authorities reportedly planned to interrogate Tsarnaev, the lone surviving suspect in the twin blasts, without informing him of his Miranda rights to remain silent and have a lawyer present, officials said the 19-year-old’s medical condition has to this point precluded any questioning.

“He’s in no condition to be interrogated at this point in time,” Boston Police Commissioner Ed Davis told “Fox News Sunday.’' “He’s progressing, though, and we’re monitoring the situation carefully.”

Speaking on ABC’s “This Week,” Senator Dan Coats of Indiana, a member of the Senate Select Committee on Intelligence, said Tsarnaev had sustained a gunshot to the throat, and it was questionable “when and whether he’ll be able to talk again.” Boston Mayor Thomas Menino, appearing on the same program, said “we don’t know if we’ll ever be able to question the individual.”

Tsarnaev is being treated at Beth Israel Deaconess Medical Center, where he is in serious condition, according to the FBI.

If Tsarnaev survives, most legal specialists predicted prosecutors would seek the death penalty, but they said the decision would probably take months. Massachusetts does not permit the death penalty for defendants charged in state courts, but federal prosecutors can seek capital punishment for crimes that include the deadly use of weapons of mass destruction.

Attorney General Eric Holder Jr. would make the final decision whether to seek the death penalty, after a recommendation from the US attorney. That process typically takes three to 18 months, said David Hoose, a Northampton lawyer who has represented defendants in federal capital cases.

Defendants in potential death penalty cases receive two appointed lawyers, one of whom must have experience in defending capital cases. In Massachusetts, the US attorney has traditionally appointed a committee to hear defense arguments on why the defendant does not deserve the death penalty. That committee then makes a recommendation to the US attorney.

Justice Department officials hear arguments from defense counsel again before making a recommendation to the attorney general.

“It's a very detailed, thorough review of all aspects of the case,’’ Hoose said, noting that the process determines what “the punishment is going to be before we get to guilt or innocence.’’

Federal death penalty cases are unusual, Hoose said. Under Presidents Bill Clinton and George W. Bush, just one in five cases that came under review were ultimately pursued as capital crimes, he said. Under the Obama administration, that figure has dropped to one in 20.

Hoose, who is preparing for a federal capital case scheduled to begin trial in Providence in August, said all but one of the previous capital cases he was involved in either resulted in plea agreements or the US attorney general declining to pursue the death penalty.

On Sunday, a number of political leaders said the case warranted the death penalty.

“I think there’s going to be a great deal of evidence put together to be able to convict him, and it should likely be a death penalty case under federal law,” said Dianne Feinstein, chairman of the Senate Intelligence Committee, during an appearance on “Fox News Sunday.’’

On CNN, Senator Charles Schumer, a New York Democrat, said: “Given the facts that I’ve seen, it would be appropriate to use the death penalty in this case.”

But Boston’s Cardinal Sean P. O’Malley said he opposes the death penalty if the suspect is found guilty of the bombings.

“There are other ways of punishing people, and protecting society, without killing them,” he said after delivering the homily Sunday at the Cathedral of the Holy Cross.

Prosecutors may also pursue capital charges as leverage to gain Tsarnaev’s cooperation and potentially secure a guilty plea, observers said.

“I’m sure they are very mindful that the threat of a death sentence could be the key to his willingness to cooperate,” said Rosanna Cavallaro
, a law professor at Suffolk University.

While a trial could provide closure and a sense of justice, it would also be “incredibly painful” for the bombing victims and their families, she said.

After Tsarnaev was taken into custody, federal officials decided against reading him his Miranda rights. Ortiz cited the public safety exemption “in cases of national security.”

In recent years, specialists said the Justice Department has argued that the length of time and scope of questions that fall under that exception are broader in terrorism cases than what is usually permissible. But civil libertarians have opposed the broader interpretation, saying it undermines the rights of defendants.

Anthony Romero, executive director of the American Civil Liberties Union, said he believed authorities could withhold Miranda to ask whether there were any more bombs hidden in Boston. Beyond that, the government must not “cut corners,’’ he said.

“Each time the administration uses this exception, it stretches wider and longer,” said Vincent Warren, the group’s director.

Miriam Conrad, the federal defender for Massachusetts, told the Associated Press her office expects to represent Tsarnaev and said he should have a lawyer appointed.

Stephen G. Huggard, a Boston criminal defense lawyer and former federal prosecutor, said the lack of charges so far may reflect an effort to extract intelligence from the suspect before he has a lawyer.

“Once they charge him, he’s going to have a lawyer, and [prosecutors] may want to keep the playing field to themselves for a couple of days,” said Huggard, a former official in the Justice Department and US attorney’s office.

If Tsarnaev provides evidence before the Miranda warning, defense lawyers would aggressively seek to have that evidence suppressed. But prosecutors might be willing to risk that if officials think the intelligence is more valuable.

“The question becomes, ‘Are you more interested in the criminal case or are you more interested in the intelligence gathering, and do you think you can prove the criminal case with what you have?’ ” Huggard said.

Bryan Bender, Kathy McCabe, and Milton Valencia of the Globe staff contributed to this report. Peter Schworm can be reached at schworm@globe.com. Follow him on Twitter @globepete.

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